Fundamental doubts on the nature of representation constitute the essential theme of Castellucci’s work. The paper analyzes how, through very specific scenic devices, he confronts spectators not only to the power of theater but also its tremendous darkness. Exposed to violent sensible impressions and pure vibrations (sounds, odors, ruptures of rhythm), the spectator is forced to see beyond the image and to think the unthinkable. It is argued that what constitutes the genuine elements of such a theater is what Deleuze, and before him Artaud and Proust called “signs”. Signs testify for the power of nature and spirit working beneath words, gestures, characters or represented actions. Far from being simply linked to a signifying expression, a content or to an affection of the subject, they are above all a manifestation of forces, of a differential of intensity. With that regard, on the one hand signs are always sensible, already part of a process of actualization, but on the other hand they already point towards the virtual system of relations, the ideal coordinates of a problem. It is the reason why signs are always to be interpreted, and put our thought in motion. There is a great danger in this interpretation however, since signs are deadly when they are lost in the distance (they do not touch us, they do not reveal the nature of the problematic), but also when they strike us with full force (they abruptly reveal the unbearable abyss, and lead the one confronted to them to madness or death). The art of Castellucci (originating from Greek tragedy) is precisely to torn spectators apart between these two kinds of signs. The questioning we would like to undertake is hence very simple: what is the origin of these signs, where one finds the maximum drama in the least possible information? why do they manage to make such a deep impression on us? or, as Castellucci himself puts it about his experience of listening Schubert: “where do my tears come from, void of content and so far removed from the sentimentality I loathe?”. Paradoxically, isn’t it because signs withhold force that they express their potency, beyond any theater of representation, any explicit content, and any meaning? Therefore, we believe Castellucci prominently displays the new image of thought Deleuze is promoting in all of his works: the will not to have the choice anymore, the spirit forced by sensation, the need for thought to go as far as the tremendous darkness, but also the need to interpret signs, to elevate ourselves from this darkness to light. While projecting images from Castellucci’s productions (Parsifal, Orphée et Eurydice, Schwanengesang D744, Go down Moses, On the concept of the face of the son of God, Ödipus der Tyrann, Human use of human beings) we question to what extent spectator cannot genuinely see without being seen in return, why that which is worth being represented is always the irrepresentable, and, ultimately, address the main problem Deleuze was obsessed with: the sensible origin of thought.